1. Field of the Invention
The present invention relates generally to a method of manufacturing microfluidic chips for handling fluid samples on a microfluidic level, and, more specifically, to a method of continuously manufacturing microfluidic chips for handling fluid samples on a microfluidic level and microfluidic chips manufactured using the same. The manufactured microfluidic chips can be used to perform analysis, for example, polymerase chain reaction (PCR) analysis.
2. Discussion of the Related Art
Microfluidics refers to the technology that relates to the flow of liquid in channels of micrometer size. At least one dimension of the channel is of the order of a micrometer or tens of micrometers to be considered as microfluidics. Microfluidics can be used in medicine or cell biology researches.
Microfluidic devices are useful for manipulating or analyzing micro-sized fluid samples, with the fluid samples typically in extremely small volumes down to less than pico liters. When manipulating or analyzing fluid samples, fluids are continuously flowed onto microfluidic chips or pumped onto microfluidic chips in doses.
A microfluidic chip includes at least one channel in a chip-shaped substrate. During manipulation or analysis of the fluid, the fluid is introduced into the channel. Typically, one end of the channel is an inlet through which the fluid enters, and another end of the channel is an outlet through which the fluid exits. Additionally, one or more valves can be along the channel pathway to control the movement of the fluid. For example, a microfluidic chip can include various functional units performing predetermined functions using the fluid and the valve(s) can limit or hold the fluid within a particular unit for a predetermined manner prior to the fluid being injected to another particular unit.
Presently, microfluidic chips have micro-channels are manufactured in batches. First, a design channel is made. Then, a mold reflecting the channel design is made. Using the mold, the channel design in imprinted in PolyDiMethyiSiloxane (“PDMS”) block, and a glass slide is bonded over the micro-channels and on the PDMS block to seal the micro-channels. Such microfluidic chip is made one at the time to replicate the channel design in the mold.
FIG. 1 is a flow illustration of steps for manufacturing a microfluidic chip mold according to the related art, and FIGS. 2A-2D are perspective views of the manufacturing of a microfluidic chip mold according to the related art. The manufacturing of a microfluidic chip according to the related art takes a channel design and duplicates the channel design onto a photomask 10.
As shown in FIG. 1 and FIG. 2A, a photoresist 22 is deposited onto a semiconductor wafer 20. As shown in FIGS. 1 and 2B, the photomask 10 that reflects the channel design 12 is then placed over the wafer 20, and the wafer 20 with the mask 10 undergoes UV exposition to cure the photoresist 22. Then, as shown in FIGS. 1 and 2C, the wafer 20 with the cured photoresist 22′ is developed. The ‘negative’ image of a channel according to the channel design is etched away from the semiconductor wafer 20. As shown in FIGS. 1 and 2D, after all residual photoresist are removed, the resulting wafer becomes a mold 20′ that provides the channel according to the channel design 12′.
FIG. 3 is a flow illustration of steps for manufacturing a microfluidic chip according to the related art, and FIG. 4 reflects perspective views of the manufacturing of a microfluidic chip according to the related art. The manufacturing of a microfluidic chip according to the related art takes the mold and makes microfluidic chips in batches.
As shown in FIG. 4, the mold 20′ may first be clean. As shown in FIGS. 3 and 4, PDMS in liquid form 30 is poured onto the mold 20′. Liquid PDMS 30 may be mixed with crosslinking agent. The mold 20′ with liquid PDMS 30 is then placed into a furnace to harden PDMS 30. As shown in FIGS. 3 and 4, as PDMS is hardened, the hardened PDMS block 30′ duplicates the micro-channel 12″according to the channel design. The PDMS block 30′ then may be separated from the mold 20′. To allow injection of fluid into the micro-channel 12″(which will subsequently be sealed), inlet or outlet is then made in the PDMS block 30′ by drilling into the PDMS block 30′ using a needle, as shown in FIGS. 3 and 4.
Then, as shown in FIGS. 3 and 4, the face of the PDMS block 30′ with micro-channels and a glass slide 32 are treated with plasma. Due to the plasma treatment, the PDMS block 30′ and the glass slide 32 can bond with one another and close the chip, as shown in FIGS. 3 and 4.
To manufacture a microfluidic chip according to the related art involves first manufacturing a master mold and then, separately duplicating channel designs onto PDMS. The related art method would require manufacturing microfluidic chips in batches, and the output rate based on this related art method is limited by the number of master molds. Thus, there continues to exist a need for developing a method of manufacturing microfluidic chips that manufactures microfluidic chips continuously, and that is quick, simple, reliable and cost effective.
Therefore, what is needed is a method of manufacturing that can continuously, reliably and quickly form micro-channels in chips, so that it is more cost effective to manufacture microfluidic chips. Also needed is a method of manufacturing microfluidic chips that is more flexible in adopting different micro-channel designs and can quickly adopt a different micro-channel design in a consistently controlled manner.